Circuit interrupter



March 20, 1945. w LEEDS CIRCUIT INTERRUPTER Filed Aug. 12, 1942 3Sheets-Sheet l INVENTOR 4 Mh/brap/Wleedg, BY

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M In w March 20, 1945. w LEEDS 2,372,094

CIRCUIT INTERRUPTER Filed Aug. 12, 1942 3 Sheets-Sheet 2 42/ 125 7Mae/vial 4 9 INVENTOR M'n/hrap/W, Z 6e03,

March 20, 1945. w LEEDS 2,372,094

CIRCUIT INTERRUPTER Filed Aug. 12, 1942 3 Sheets-Sheet 5 wmuzssss;INVENTO'R 54 W'l/v 4 a. M23 55 5 ATTOR Y Patented Mar. 20, 1945 CIRCUITINTERRUPTER Winthrop M. Leeds, Wilkinsburg, Pa., assignor toWestinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., acorporation of Pennsylvania Application August 12, 1942, Serial No.454,514

20 Claims.

This invention relates to circuit interrupters in general, and, moreparticularly, to a method and structure for effecting the rapidextinction of alternating current arcs. More specifically the inventionconcerns alternating current circuit interrupters of the type wherein analternating current arc is drawn in an elongated slot or passage andtherein subjected to the deionizing action of gaseous or liquidparticles.

More particularly, the present invention is concerned with an arcextinguishing structure which establishes an alternating current are inan elongated passage and causes the lateral oscillation of said are bymagnetic means.

The lateral oscillation of the arc may be caused by the use of aunidirectional magnetic field. One or more permanent magnets may beemployed suitably shaped and o disposed within the arc extinguishingstructure in relation to the arc that the arc is constantly under theinfluence of a unidirectional magnetic fleld. It will be evident,therefore, that in an alternating current circuit interrupter utilizingone or more of such permaneni; magnets the arc stream will be forcedlaterally in one direction during one half cycle of the alternatingcurrent wave, and forced laterally in the opposite direction during asubsequent half cycle in the alternating current wave. Obviously adirect current magnet could be used in placeof the permanent magnets tocreate the unidirectional magnetic field.

The lateral oscillation of the arc stream may also be produced byopposing magnetic and gas blast forces, each acting in a constantdirection but first one and then the other predominating in magnitude.The magnetic force in this case may be produced by suitably shapedplates of magnetic material, such as iron, suitably disposed adjacent tothe arc stream. The lateral gas blast may be obtained by utilizing thegaseous products of decomposition generated by the arc itself anddirected by suitably shaped insulating plates forming the walls of thearcing chamber.

More particularly, my invention concerns an improved method of arcinterruption comprising simultaneously establishing and lengthening analternating current arc, providing for a lateral oscillation of saidare, the oscillations being such that during the lateral movement of thearc in one direction a suitable arc extinguishing gas is generated bythe arc, and during the subsequent lateral movement of the arc in theopposite direction the arc is located in the most favorable position forinterruption by a turbulent blast from the gas formed during theprevious lateral movement of the arc.

My invention is also concerned with an improved method of arcinterruption which comprises simultaneously lengthening and oscillatingthe alternating current are in an arc extinguishing medium.

The main object of my invention is to provide an improved structure forthe interruption of alternating current arcs.

It is also an object of my invention to provide in the improved arcextinguishing structure oi my invention an improved method of arcinterruption as outlined above.

It is also an object of my invention to draw an alternating current arein an elongated slot or passage, and to laterally oscillate said arewith a frequency substantially equal to the frequency of the alternatingcurrent circuit being interrupted. Because of the consecutive alternatedirection of the lateral arc motion favorable conditions are obtainedfor most efiectively bringing into play the extinguishing influence ofgaseous or liquid particles.

Another object is to provide in either an airbreak or a liquid-breakalternating current circuit interrupter one or more permanent magnetssuitably shaped and so disposed in relation to the arc stream as tofurnish a unidirectional magnetic field across said are stream.

Another object is to provide in either a liquidbreak or an air-breakcircuit interrupter a plurality of U-shaped permanent magnets, themagnets being disposed in pairs substantially surrounding the arcingslot with like poles lying adjacent one another to furnish aunidirectional magnetic field transversely of the arcing slot. Gas isproduced during the lateral motion of the arc in one direction, by thearc itself acting upon gas-evolving material or upon a suitable liquid,such as oil, and during the subsequent lateral movement of the arcstream the arc is located in the most favorable position forinterruption by a blast of gas formed by the arc itseli during theprevious lateral movement or the arc.

Another object is to provide a pair of interrupting structures of thenarrow slot type closely positioned with respect to one another, so thatarcs may be extinguished alternately in one of said structures and thenin the other of said structures, in effect doubling the life of theinterrupter over that of the separated individual structures.

Another object is to provide a pair of cooperatin: structures of thenarrow slot type and to use in conjunction therewith a movable contactof such shape th'airthe are tube interrupted in the twin structure willbe extinguished just about as many timesm one oi. said cooperatingstruetures a in the other, thus doubling the life of the combinedinterrupting structure.- V

completely from one of the separate. structures to the other, thusutilizing the combinedinter rupting capacity of both structures.

Another object is to use in a twin structure 01' the toregoing type amovable contact with two conducting buttons fixed thereon, so that asone of said buttons is worn down when only one of the structures is usedduring an interrupting operation, upon a subsequent opening of theinterrupter the arc will be drawn at the other conducting button toutilize the structure which was not previously used.

Another object is to use a twin structure similar to the foregoing ofeither the air-break or liquid-break type, in-whlch is provided one ormore substantially U-shaped plates composed of a magnetic materialsurrounding the arcing slots of both structures, to bias the arc intoone or the other of said structures depending upon the location of saidare when initially drawn.

I am well aware that my invention is applicable to air-type circuitinterrupters in which a gaseous arc extinguishing medium is produced bythe utilization of gas-evolving material. However, merely for purposesof illustration only I describe ,my invention in connection with its usein liquid breakers of the oil immersed type.

Further objects and advantages of my invention will become apparent upona consideration of the following description taken in connection withthe accompanying drawings, in which:

Figure 1 is a side elevational view, partially in section, of a liquidtype circuit interrupter constructed in accordance with the principlesof my invention and shown in the closed-circuit position;

Fig. 2 is an enlarged cross-sectional view of one of the grid structuresshown in Fig. 1 and taken along the line II-lI of Fig. 1 looking in thedi-* rection of the arrows at a time when the movable contact hasseparated from the stationary contact thus drawing an arc therebetween;

Fig. 3 is a fragmentary cross-sectional view of the grid structure shownin Fig. 2 taken along the line II[III of Fig. 2 and looking in thedirection of the arrows;

Fig. 4 is a cross-sectional view of the top fiber plate shown in Fig. 2taken on the line IVIV of Fig. 2 with the tie rods 29 omitted;

Fig. 5 is an enlarged plan View of one of the fiber plates used in thegrid structure of Fig. 1;

Fig. 6 is a cross-sectional view of the fiber plate shown in Fig. 5taken on the line VI-VI of Fig. 5;

Fig. 7 is an enlarged plan view of the top fiber plate used in the gridstructure shown in Fig. 1;

Fig. 8 is a side elevational view of the top fiber plate shown in Fig.'7;

Fig. 9 is an enlarged plan view of the bottom fiber plate used in thegrid structure of Fig. 1;

Fig. 10 is a side elevational view of the bottom fiber plate shown inFig. 9;

Fig. 11 shows two curves of arc current and magnetic force actingthereon in the circuit interrupter shown in Fig. 1;

Fig. 12 is a side elevational view, partly in secaaraoaa v p tion of acircuit interrupter embodying a modificatlon or-my invention and shownin the closedcircuit position;

13 is air-enlarged crossesectional view or- 5i one of the gridstructures shown in Fig. 12 taken along the line XIII--X1l1lfbf 12andlooking in thedirection of thearrow;..,

Fig. 4is :airagmentary cross-sectional view of the grid structure shownin Fig. 13 taken along 10 the line XIV-XIV'of Fig. 13 and looking in thedirection .of the arrows;

Figs,,l5 through -20are enlarged plan and side views of fiber platesused in one or the gridstructures shown in Fig. 12;

magnetic inserts used in the grid structure shown inFig. 12; Y

Figs. 22, 22A and 22B consist of three enlarged fragmentary views of theend of the movable contact shown in Fig. 12;

Fig. 23 shows two curves of arc current and the lateral magnetic forceacting thereon as a function of time, these curves being illustrative ofaction taking place in the interrupter shown in Fig. 12;

Fig. 24 is an elevational view, in central longitudinal section, of amodified type grid embodying the principles of my invention;

Figs. 25 through show plan and side views 80 of fiber plates used in thegrid shown in Fig. 24;

Fig. 31 is a cross-sectional view taken along the line )DKXI-XXXI ofFig. 24; and

Figs; 32 and 33 show the configuration of the end of the movable contactused in the grid 35 shown in Fig.24.

Referring to Figs. 1 to 11 inclusive, and more particularly to Fig. 1,the reference numeral I designates a tank structure containing asuitable arc extinguishing liquid 3, such as oil, in

which is immersed two serially related grid structures, each of which isindicated generally by the reference numeral 5. The two grid structures5 are supported from a cover 1 by means of the terminal bushings 9 andthe stationary contact structures ll, I2 which may be of anyconventional design. The external terminals I3, I 5 are used to connectthe circuit-interrupter into the circuit to be controlled.

The circuit interrupter is operated by means of the reciprocatinglongitudinal movement of an insulating lift rod 11, at the lower end ofwhich is a conducting bridging member l9. At the ends of the conductingbridging member l9 are two movable contacts 2 I, 23 of blade-likeconfiguration, which cooperate with two stationary contacts 25, 21 toopen and to close the electrical circuit through the breaker.

When the breaker is in the closed-circuit position, as is illustrated inFig. 1, the electrical circult therethrough consists of the externalline terminal l3, the stationary contact structure II, the stationarycontact 25, the movable contact 2|, the conducting bridging member l9,movable contact 23, stationary contact 21, stationary contact structurel2 and external line terminal [5.

Each of the grid structures 5 comprises a plurality of fiber platescompressed together by suitable tie rods 29, and spaced a properdistance below the stationary contact structures ll, l2 by the spacingsleeves 3 I. I

The top fiber plate 33 of each grid structure 5 is more clearly shown inFigs. 7 and 8. The top fiber plate 33 contains apertures 35 for thereception of the tie-rods 29, and a central aperture 31 through whichextends the stationary Fig. 21 is an enlarged plan View of one-of thecontact 25, or 21 which may be resiliently mounted. The clearance isslight between the stationary contact 25 or 21 and the central aperture31 in the top fiber plate 33, the purpose for which will appear morefully hereinafter.

The bottom fiber plate in each of the two grid structures is designatedby the reference numeral 39, and is shown more clearly in Figs. 9 and10. The bottom fiber plate 39 has bored therein apertures 35 for thereception of the tierods 29, and is also provided with a rectangularcentral aperture 4|, through which moves the movable contact 2| or '23,as the case may be.

It will be noticed that again there is very slight clearance between therectangular central aperture 4| and the movable contact 2| or 23, thepurpose for which will also appear hereinafter.

Immediately below the top fiber plate 33 (see Fig. 3) are a plurality,in this instance six, fiber plates 43, more clearly shown in Figs. 5 and6,

and herein designated pocket plates. These fiber plates 43 aredesignated pocket plates-because each of them is provided with a seriesof pockets 45. When the grid structure 5 is immersed in the liquid 3,the pockets 45 serve to retain adjacent the arc path a readily availablequantity of liquid, such as oil, upon which the arc may react. Thepocket fiber plates 43 also are provided with apertures 35 toaccommodate the tie-rods 29. It will be noticed that the pocket fiberplates 43 are also provided with a throat portion 41, which leads into aflared vent opening 49, as more clearly seen in Fig. 5.

Immediately below the top group of six pocket plates 43 is a fiberinsert plate 5|, the configuration of which is more clearly shown inFigs. 2 and 4. It will be noticed that the fiber insert plate 5|contains two U-shaped permanent magnets 53, 55 inserted in the fiberinsert plate 5|, the purpose for which will appear more clearlyhereinafter. The two U-shaped permanent magnets 53, 55 are inserted inthe fiber insert plate 5| with the two north poles lying adjacent oneanother and the two south poles lying adjacent one another, as indicatedin Fig. 2. It will therefore be apparent that a unidirectional magneticfield is provided between the two north poles and the two south poles,said unidirectional magnetic field extending substantially transverselyacross an arcing slot 51. It will be noticed in Fig. 2 that the arcingslot 51 narrows somewhat at 59 in the insert plate 5| and is closedtherein. The restriction 59 serves to hold the higher current arcsduring the peak of the alternating current wave, when theircross-sectional areas are large, outside of the restriction 59 in thewidened portion of the slot 51. But near a current zero, when thecross-sectional area of the higher current arc is relatively small, thenit will enter the restriction 59. The smaller current arcs with theirsmaller cross-sectional areas may, however, freely enter the restriction59 even during the peak of the current wave. The arcing slot 51 isvented to the left in the pocket plates 43.

When all the fiber plates are assembled upon the. tie-rods 29 in theirrespective groupings, as shown in Fig. 3, it will be observed that allof the apertures 35 align for the accomodation of the tie-rods 29, and,as more clearly shown in Figs. 2 and 3, the fiber plates form thelongitudinal arcing slot 51.

When the insulating lift rod 1 is moved downwardly to separate themovable contacts 2i, 23'

from the stationary contacts 25, 21 two serially related arcs are drawn.Considering onl the are drawn between between the stationary contact 25and the movable contact 2|, in the left hand rid structure 5 as viewedin Fig. 1, it will be apparent that the arc, designated by the referencenumeral 53, will be drawn in the arcing slot 51, and therein subjectedto the influence of the strong unidirectiona magnetic field produced bythe pairs of U-shaDed permanent magnets 53, 55.

'Let it be supposed that during the first half cycle of arcing theinstantaneous current in the arc 53 is flowing upward from the movablecontact 2| to the stationary contact 25 in the left hand grid structure5 of Fig. 1. The direction of the unidirectional magnetic field willthen be such as to force the are 53 to the right, as indicated by thearrow 55 in Fig. 2. Since liquid, in this instance oil, is disposedwithin the arcing slot 51,'and also retained in the pockets 45, the are53 will react upon the oil in the right hand end of the slot 51, asviewed in Fig. 2 to produce a considerable quantity of gas. Since thereis slight clearance between the stationary contact 25 and the centralaperture 31 in the top fiber plate 33, and also slight clearance betweenthe movable contact 2| and the rectangular central aperture 4| in thebottom fiber plate 39, the gas which is produced by the action of theare 53 on the oil contained in the right hand end of the arcing slot 51must be vented sooner or later out of the left hand end of the slot 51,as viewed in Fig. 2.

When the instantaneous current in the first half cycle of arcingdecreases, the are 53 will begin to retreat toward the middle of theslot 51 where it was initially drawn, due to the force of the expandinggases produced by the are 53 when it was in the right hand end of theslot 51. When the instantaneous current reaches zero, that is, at thefirst current zero of the arcing period, there is a good opportunity forthe extinction of the are 53, as the gas streams through the arc towardthe left, cooling the arcing space, and carrying away ionized particles.

If the are 53 restrikes, the instantaneous current during this halfcycle will be in the opposite direction than the direction consideredabove during the first half cycle of arcing. Now the direction of theinstantaneous current will be such that theunidirectional magnetic fieldwill force the are 53 to the left, as viewed in Fig. 2, towardthe narrowrestriction 59 in the fiber insert plate 5| of Fig. 2. However, the are63 will be retained within the arcing slot 51 because the slot 51 in thefiber insert plate 5| is closed at its left-hand end, as viewed in Fig.2. The are 53, is, consequently, held in the constricted space 59 in thefiber insert plates 5| and in the throat portion 41 of the pocket fiberplates 43.

During the second half cycle of arcing when the arc 53 is forced by theunidirectional magnetic field to the left, as viewed in Fig. 2, it willbe noted that the are 53 is placed at the most favorable position forinterruption by a turbulent blast of gas which was generated by the are53 itself during the previous half cycle of arcing. During the peakvalue of instantaneous current of the second half cycle of arcing, whenthe are 53 is at the extreme left hand end of the arcing slot 51, itwill be noticed that the width of the throat 41 formed in the pocketfiber plates 43 is such that there is sufiicient space on both sides ofthe arc stream 53 to permit a relatively free passage of gas, oilparticles, and oil out of the arcing slot 51 through the flared openings49, on both sides of the are 63.

Consequently, the continuity of the arc stream 63 during the peak valueof instantaneous current is not unnecessarily disturbed, but as theinstantaneous current during the second half cycle of arcing decreases,the lateral streaming of gas, oil and oil particles to the left adjacentthe arc column becomes more efiective to cause rapid deionization of thearc space, raising the dielectric st th at current zero so that the arc63 will not restrike. Since the are 63, during high instantaneous valuesof arcing current, does not receive the full efiect of a lateral blastof gas 1 at the center of the arc column, there is a correspondinglowering of the arc voltage and less decomposition of oil as compared toconditions in a more restricted slot construction.

Should the are 53 restrike for a third half cycle of arcing, it wouldthis time be thrust to the right by the unidirectional magnetic field.The ionized gas which was produced during the first half cycle ofarcing, when the are 63 was forced to the right, will have had someopportunity to recombine with the oil disposed in the pockets 45 of thepocket fiber plates 43 before the arc 63 during the third half cycle ofarcing is again forced to the right hand end of the arcing slot 51,repeating the process described above. Since the are 63 is beingcontinuously lengthened by the downward motion of the movable contact 2Ithis brings about conditions more favorable for extinction at eachsuccessive current zero until interruption is obtained.

Cobalt steel permanent magnets may be designed which may be exposed toalternating currents of 5,000 to 10,000 amperes without beingdemagnetized. Therefore, there need be no danger that the unidirectionalmagnetic field produced by the U-shaped permanent magnets 53, 55 will beweakened by currents of magnitudes which the breaker was designed tointerrupt.

As previously mentioned above, it is essential for the best operation ofthe breaker that the top of the grid structure 5 around the stationarycontact be completely enclosed, and that the bottom of the stack alsohave an aperture only large enoughto just admit the moving contact 2 I.With such a construction the vertical flow of gas and oil is reduced toa minimum, and the lateral flow of the gas and oil is correspondinglyincreased, which lateral flow helps in the extinction of the are 63.

It will be apparent to one skilled in the art that instead of using anoil breaker with the fiber plates 43 and 5|, my invention may well beincorporated in an air-type circuit breaker which utilizes gas-evolvingplates composed of horn fiber, boric acid or other gas-evolvingmaterial. The lateral motion of the are 93 could be used to engage thearc 93 with the plates composed of gas-evolving material to produce therequisite amount of arc extinguishing fluid necessary for interruptionof the are 93. My invention is also applicable to breakers of thecompressed fluid type.

A direct current magnet may be used to produce a unidirectional magneticfield across the arcing slot 9'8 instead of using the U-shaped permanentmagnets 53, 95 as shown. The latter arrangement is preferable inasmuchas it is simpler and free of circuit connections which would have to beinsulated from the high voltage part of the interrupter.

Fig. 11 shows a cycle of the alternating current I through the are 63 asa function of the time. The curve F represents the magnitude of themagnetic force acting laterally on the are 03. The magnetic force isequal to a constant times the first power of the instantaneous current,and therefore holds up very well in the neighborhood of the current zeroperiods as shown in Fig. 11.

I Referring to the breaker embodying my invention shown in Figs. 12 to22 inclusive, and more particularly to Fig. 12, the reference numeral 61designates a tank containing a suitable arc extinguishing liquid 69, inthis instance oil, in which are submerged two grid structures, generallydesignated by the reference numerals II, I3.

A coverJ5 for the tank 61 supports two terminal reception of thetie-rods I03.

bushings 11, 19 from which depend the stationary contact structure 8 I,83.

The cover contains a central aperture through which extends theinsulating lift rod 81 carrying a conducting bridging member 89 at theends of which are securely mounted the movable contacts 9I, 93. Themovable contacts 9I, 93 engage in the closed-circuit position of thebreaker, as shown in Fig. 12, the stationary contacts 95, 91. Externalline terminals 99, I0! are provided to connect the breaker in thecircuit to be interrupted. In the closed-circuit position as shown inFig. 12, the electrical circuit through the breaker includes the lineterminal 99, stationary contact structure 8|, stationary contact 95,movable contact 9! conducting bridging member 89, movable contact 93,stationary contact 91, stationary contact structure 83, and externalline terminal IOI.

Each of the grid structures II, I3 comprises a plurality of fiber platescompressed together by tie rods I03. In each grid structure there may beprovided three types of plates. Referring particularly to Fig. 14 thetop fiber plate shown therein is called a fiber guard plate I05 and ismore clearly shown in Figs. 17 and 18. It will be noticed that the fiberguard plate I05 isprovided with four circular apertures I 01 for the Thefiber guard plate I05 also is provided with a slot, generally indicatedby the reference numeral I09 which vents into a passage III. The passageIII itself vents into a flared opening H9, the purpose for which willappear hereinafter.

Immediately below the top fiber guard plate I 05 is a fiber insert plateII5, more clearly shown in Figs. 15 and 16. The fiber insert plate II5contains a C-shaped plate II'I composed of magnetic material, in thisinstance iron, the configuration of which is shown more clearly in Fig.21. The fiber insert plate II5 i formed for the insertion of themagnetic plate II'I therein, and therefore to distinguish it from theother plates forming the grid structure "II, it is herein designated asan insert plate. The fiber insert. plate II5 contains circular aperturesI01 for the reception of the tie rods I03. The fiber insert plate H5 isformed with a slot I09 identical to the slot I09 provided in the topfiber guard plate I05 previously described. Immediately below the fiberinsert plate 5 is a second fiber guard plate I09. The two fiber guardplates I05 protect the magnetic plate II! from the action of the aredrawn in the grid structure II. Therefore, they are herein designated asguard plates.

Immediately below the second fiber guard plate I 05 are a plurality, inthis instance four, fiber pocket plates N9, the configuration of whichis more clearly shown in Figs. 19 and 20. The fiber pocket plates II9contain circular aperture I91 for the reception of the tie rods I03.They also contain a plurality, in th instance four, pockets I2I, whichas in the previous embodiment of my invention provide a readilyavailable quantity of oil adjacent the arc path. The fiber insert plateI I5 and the fiber pocket plates I I9 also contain a passage III whichleads to a flared opening II3.

Immediately below the four fiber pocket plates I I9 is a second groupingof two fiber guard plates I95, between which is a fiber insert plateII5, as more clearly shown in Fig. 14. Below this second grouping thesuccessive groupings of plates down to the bottom of the grid structure1| are repeated as previously described.

The ends of the movable contacts 9|, 93 are identical, and Fig. 22 showsthe configuration of the end of the movable contact 9|. It will benoticed that at the extremity of the movable contact "9| is a conductingsupport member I23 disposed at right angle to the movable contact 9| andat the ends of which are two upstanding rounded contact buttons I25,I21, the purpose for which will appear hereinafter. When the breaker isin the closed position, as is illustrated in Fig, 12, the roundedcontact buttons I25, I21 engage in abutting relation the stationarycontact 95, which may be a fiat plate of metal resiliently mounted.

when the fiber plates are assembled upon the tie rods I03, the passagesIII, the flared openings H3 and the slots I99 align to form alongitudinal arcing slot indicated by the reference numeral I29 in Fig.13. During the operation of the breaker the movable contact 9| moveslongitudinally of the slot I3I shown in Fig. 13, created by thealignment of the passages III and openings H3 in the fiber plates.

The pockets I2I in the fiber pocket plate 9 retain a sufllcient quantityof readily available oil along the walls forming the arcing slot I29.

The manner in which the breaker operates will now be described. When itis desired to open the circuit passing through the breaker, or whenexternal overload conditions requre the breaker to be opened, suitablemechanism, not shown, may be actuated to move the insulating lift rod 81in a downward direction as viewed in Fig. 12. The movable contacts 9|,93 separating respectively from the stationary contacts 95, 91 will drawtwo serially related arcs, one are in each grid structure.

As was mentioned previously the stationary contacts 95, 91 may be in theform of fiat metallic plates resiliently mounted to withstand the shockof closing. The contact buttons I25, I21, provided at the ends of themovable contacts 9|, 93. engage the fiat metallic plates constitutingthe stationary contacts 95, 91 in abuttin relat on durin theclosed-circu t position of the breaker. It will be apparent, therefore,that by the provision of two contact buttons I25, I21, the are drawnwill be drawn between the stationary contact and one of said buttons.

Consider only the grid structure 1|. Assume that the direction of theinstantaneous arcing current drawn in the grid structure 1| i in adownward direction, as v ewed in Fig. 12 and as indicated by the X inFig. 21 and that it is increasing in magnitude. Assume further that thearc I33 (see Fig. 21) drawn in grid structure 1| is drawn between thestationary contact 95 and the contact button I21. It will therefore bedrawn of! center in grid structure 1| and pos tioned slightlv in theright hand and III of the arcin slot I29. Then as the instantaneousarcing current in the are I33 increases during the subsequent halfcycle, the magnetic flux in the iron plate II1 builds up in thedirection indicated by the arrows I35 in Fig. 21. The magnetic fieldsurrounding the are I33 is distorted by the presence of the magneticplates H1, and the arc is biased to the right looking at Fig. 21 and asindicated by the arrow I31.

With an air gap of such relative magnitude as shown at I39 in Fig. 21saturation does not occur in the iron plate I I1, and the lateralbiasing force exerted by the distorted magnetic field upon the arc I33is hence proportional to the square of the instantaneous arcing current.In other words, the lateral biasing magnetic force exerted on the are I33 follows the relation: F=kI, where F is the magnetic force actinglaterally on the arc I33, k is a constant and I i the magnitude of theinstantaneous current passing through the are I 33. Fig. 23 showsgraphically the curves I and F as a function of time.

A the instaneous current in the are I33 increases during the first halfcycle of arcing the increasing magnetic force will bias the arc I33laterally farther into the closed right hand end Ill of the arcing slotI29. It will be noticed that the presence of the two contact buttonsI25, I 21 at the end of the movable contact 9| not only draws the arcI33 off center in the grid structure 1| to avoid hesitation of the arcI33, but also the contact buttons I25, I21 assist to bring the arc I33farther into the ends of the arcing slot I29 and hence into a strongerpart of the magnetic field.

While the arc I33 is in the right hand end I4I of the arcing slot I29 itwill react upon the oil contained in the pockets I 2| in the fiberpocket plates I I9 to produce a considerable quantity of areextinguishing gas under pressure. As the instantaneous current in thearc I33 decreases near the end of the first half cycle of arcing, thelateral biasing magnetic force will correspondingly decrease until thepressure of the gas in the right hand end I of the arcing slot I 29overcomes the magnetic force to throw the arc I33 back toward the centerof the arcing slot I29. adjacent the slot I3I (see Fig. 13).

It will be observed that the magnetic force is a function of the secondpower of the instantaneous current through the arc I33, and thereforewill drop considerably in magnitude near the end of the first half cycleof arcing (see Fig. 23) to readily permit the expansive force of thedecomposed oil gases to carry the arc I33 back toward the center of thearcing slot I29 adjacent the pars sages I II in the fiber platesconstituting the grid structure. At this position the are I33 has arelatively small cross-section, because of the low me anitude ofinstantaneous arcing current at this time, and the streaming of gas andoil particles past the centrally positioned are I 33 and out the ventpassages I I I in the fiber plates creates a very favorable conditionfor extinction of the arc I39.

If the arc I33 is not extinguished completely at the end of the firsthalf cycle of arcing, but restrikes, it may do one of two thingsdepending upon its position. If it is off-center and slightly to theright, looking at Fig, 21, it may be drawn back toward the closed endIll of the arcing slot I 29 to repeat its former movement. Thedecomposed oil gases which were left in the right hand end I of thearcing slot I29 will have had some chance to mix with fresh oil retainedin the pockets I 2| in the fiber pocket plates 9 to be ready for thenext onslaught. It will be noticed that the force F in Fig, 23 ispositive during both half cycles of arcing current to indicate that thearc I33 was again forced to repeat its former movement into and out ofthe right hand end I4! of the arcing slot I29. This lateral movement ofthe arc I33 into and out of the right hand end I of the arcing slot I29may continue until extinction of the arc I33 occurs, each time the arcI33 being thrown back toward the center of the arcing slot I29conditions favorable for extinction, as previously described,reoccurring because of the small cross-section of the arc I33 at thistime and because of the streaming of the gas and oil particles past theare I 33 in their venting through the passages III out of the gridstructure.

It may happen, however, that at any time when the arc I33 is thrown backtoward the center of the arcing slot I 29, it may be thrown so far bythe expanding force of the decomposed oil gases that it will bepositioned off-center to the left adjacent the left hand end I43 of thearcing slot I29. In this event the arc I33 will be drawn into the freshoil disposed in the left hand end I 43 of 'the arcing slot I29 becauseof the presence of the magnetic inserts II I. I33 when it is thrown backtoward the central portion of the arcing slot I29 will largely determinewhether it will repeat its movement during the previous half cycle ofarcing, or whether it will move into the opposite end of the arcing slotI 29 to engage fresh oil retained in the pockets I211. In either eventconditions are favorable for extinction at the end of any half cycle ofarcing.

It should be noticed that if only one end of the arcing slot I 29 isused during the extinction process the contact button for that end maybe worn down sufficiently so that during a subsequent opening operationof the interrupter the other contact button will leave the stationarycontact last to result in drawing the arc at the other contact button.In this manner the life of the grid structure II is prolonged byinsuring that the arc will be drawn just about as many time in one endof the arcing slot I29 as it is drawn at the other end of the arcingslot I29.

It will be observed that the direction of the magnetic flux across themain air gap I39 (see Fig. 21) is such as to keep the arc I33 fromgetting out of the grid structure II.

The embodiment of my invention shown in Figs. 24 to 33 inclusive issubstantially the same as the embodiment of my invention just described.However, a blade-like moving contact I45 is used similar to theblade-like moving contact 2| used in the interrupter shown in Fig. 1.Also in place of the C-shaped magnetic insert II'I used in the breakershown in Fig. 12, a pair of U-shaped inserts I 46 composed of magneticmaterial, such as iron, are employed.

The fiber guard plate I41 has no vent passages III as did the fiberguard plates I 0! Fig. 1'7. The fiber insert plate I 48 also hasno ventpassages III. The fiber pocket plate I49 is composed of two identicalhalves I50, which when assembled on the tie-rods I03 provide two lateralvent passages III, as more clearly shown in Fig. 31.

The grouping of the fiber plates in the grid structure H (see Fig. 24)may comprise a fiber pocket plate I 49 between two groups of plates,each group consisting of an insert plate I 48 positioned between twoguard plates Ill. The groupings may be repeated to the bottom of thegrid structure II. It is advisable to minimize the longitudinal flow ofgas and oil in this embodiment The position of the arc of my invention.Consequently the top and bottom fiber plates used in the grid structureII of Fig. 24 may provide only slight clearance between the movablecontact I 45 and the stationary contact (not shown) and aperturesprovided in the top and bottom plates (not shown) similar to the fiberplates 33 and 39 shown respectively in Figs. 7 and 9 of the interruptershown in Fig. 1.

The method of operation of this embodiment of my invention is similar tothat described in connection with the interrupter shown in Fig. 12. Byenclosing the grid structure II (see Fig. 24) more than was done withthe interrppter shown in Fig. 12, and providing restricted lateralventing through the passages III improved operation is obtained.

It will be apparent to one skilled in the art that gas-evolving fiberplates could be used in place of a liquid, and that features of myinvention may be applied to compressed-fluid interrupters. When the termfluid is used herein and in the appended claims it is meant to includegases, liquids, vapors-and sprays.

Although I have shown and described specific structures, it is to beclearly understood that the same were merely for purposes ofillustration and that changes and modifications may be made by thoseskilled in the art without departing from the spirit and scope of theappended claims.

' I claim as my invention:

1. In an alternating current circuit interrupter, means having a passagetherein vented only along one side, means for establishing an are withinsaid passage, and means for oscillating said are laterally within saidpassage with a frequency substantially the same as the circuit.

2. In a circuit interrupter for interrupting an alternating currentcircuit, means defining an arcing passage vented only along one side,means for establishing an are within said passage, and

means for oscillating said arc laterally with a frequency substantiallythe same as the frequency of said alternating current circuit, thelateral motion of the are in one direction being toward the vented sideof the passage.

3. In a circuit interrupter, means providing an arcing chamber ventedonly along one side and immersed in a liquid, relatively movablecontacts for establishing and lengthening an are within said chamber,and means for simultaneously causing the lateral oscillation of said arewithin said chamber, with a frequency substantially the same as thecircuit, the lateral motion of the arc in one direction generating gaswhich is used to facilitate the extinction of the arc.

4. In a circuit interrupter for interrupting an alternating currentcircuit, means definin an arcing slot, the slot being vented only alongone side, relatively movable contacts for establishing and lengtheningan are within said slot, an arc extinguishing liquid disposed adjacentto said arc, and magnetic means for causing the lateral oscillation ofsaid are with a frequency substantially the same as the frequency ofsaid alternating current circuit.

5. In a circuit interrupter for interrupting an alternating currentcircuit, an insulating structure comprising a plurality of insulatingplates pressed together, said insulating structure bein immersed in anarc extinguishing liquid, said insulating plates defining an arcingslot, the slot being vented only along one side, means for establishingan are within said slot, magnetic means comprising one or more plates ofmagnetic mation of said are with a frequency substantiallythe same asthe frequency of said alternating current circuit.

6. In a circuit interrupter for interrupting an alternating current,means defining an arcing passage, the passage being vented only alongone side, means for establishing an are within said passage, one or morepermanent magnets disposed adjacent said passage for creating aunidirectional magnetic field across said passage to cause the lateraloscillation of said are.

7. In a circuit interrupter for interrupting an alternating current,means providing an arcing said plates having aligned openings therein toprovide an arcing slot, one or more C-shaped plates of magnetic materialsubstantially surrounding said slot, means for establishing an arewithin said arcing slot comprising relatively movable contacts, at leastone of said contacts having two upstanding contact portions to positionsaid are initially off center within said arcing slot.

13. In a circuit interrupter, an insulating structure comprising aplurality of insulating plates,

slot, means for establishing an are within said slot, one or more pairsof U-shaped permanent magnets, each pair substantially surrounding saidslot and having like poles adjacent one another for creating aunidirectional magnetic field across said slot for oscillating said arelaterally.

8. In a circuit interrupter for interrupting an alternating current, aninsulating structure comprising a plurality of insulating platescompressed together, said insulating structure being immersed in an arcextinguishing liquid. said insulating plates forming an arcing slot,means for establishing an are within said slot, one or more pairs ofU-shaped permanent magnets, each pair substantially surrounding saidslot and disposed with like poles adjacent one another for creating auni directional magnetic field across said slot, said magnetic fieldcausing the lateral oscillation of said are within said slot with afrequency substantially the same as the frequency of said alternatingcurrent.

9. In a circuit interrupter for interrupting an alternating current, aninsulating structure comprising a'pluraiity of insulating plates, saidinsulating structure being immersed in an are extinguishing liquid, saidinsulating structure providin an arcing slot, means for establishing anare within said arcing slot, means for venting said arcing slot alongone side thereof, said venting means providing a relatively restrictedslot in which said are may be positioned during at least part of theinterrupting process, one or more pairs of U-shaped permanent magnetsdisposed adjacent said arcing slot and having like poles facing oneanother to create a unidirectional magnetic field across said arcingslot, the arrangement being such that the alternating current are whichis established within said arcin slot is oscillated laterally by saidunidirectional magnetic field, said alternating current are generatingarc extinguishing gas during one half cycle and being positioned in saidrelatively restricted slot during the subsequent half cycle to receivethe flow of said are extinguishing gas.

10. In a. circuit interrupter, insulating means defining an arcing slot,means for establishing an are within said slot, means comprisingmagnetic material substantially surrounding said arcing slot, saidarcing slot being vented only intermediate the ends thereof.

11. In a circuit interrupter, means defining an arcing slot, means forestablishing an are within said arcing slot, one or more members of C-shaped magnetic material substantially surrounding said slot to causethe lateral oscillation of said are, said arcing slot being vented onlyintermediate the ends thereof.

12. In a circuit interrupter, an insulating structure comprising aplurality of insulating plates,

said insulating plates having aligned openings to form an arcing'slot,venting means ventin said slot intermediate the ends thereof, saidinsulating structure being immersed in an arc extinguishing liquid, acontact disposed at one end of said arcing slot, a cooperating movablecontact movable through said venting means and away from saidfirst-mentioned contact, said movable contact having two upstandingconducting portions to establish and lengthen an are within said slot,one or more C-shaped members of magnetic material substantiallysurrounding said arcing slot and having their open portions adjacentsaid venting means, said C-shaped members tending to cause the lateraloscillation of said are in a direction substantially perpendicular tothe center line of said venting means, said-upstanding conductingportions functioningto position said arc initially ofi center in saidslot.

14. In a circuit interrupter, an insulating structure defining a slot,means for establishing an arc in said slot, one or more pairs ofU-shaped members composed of magnetic material disposed adjacent to saidarcing slot with the open ends of each pair facing one another, meansproviding oppo ed vent passages extending from the center of said slotto the region outside said insulating structure.

15. In a circuit interrupter, insulatin means for defining two or moresubstantially closed arc. ing slots having a common entrance portion,means for establishing an are within said entrance portion, and magneticmeans for moving said are into any one of said arcing slots. 16. In acircuit interrupter, insulating means for defining two or more arcingslots having a common entrance portion, means for establishing an arewithin said entrance portion, magnetic means for moving said are intoany one of said arcing slots, and means tending to bias said are intodiiferent arcing slots on successive opening operations for increasingthe life of said interrupter.

17. In an alternating-current circuit interrupter, means forestablishing an arc, means for establishing a unidirectional magneticfield for causing a lateral oscillation of the arc, gas producingsubstance with which the arc contacts during its lateral movement in onedirection to produce gas, the produced gas facilitating the extinctionof the arc during its lateral movement in the opposite direction.

18. In an alternating current circuit interrupter, means forming a, slothaving a restricted portion, means for establishing an are within theslot, means for providing a unidirectional magnetic field for causing alateral oscillation of the are within the slot, gas producing substancewith which the arc contacts during its lateral movement in one directionto produce gas, the are being forced into the restricted portion duringits lateral movement in the opposite direction, the produced gasfacilitating the extinction of the arc after the latter has been forcedinto the restricted portion.

19.In an alternating current circuit inter rupter, means forming a slothaving a relativelyducing substance with which the arc contacts 10during its lateral movement in one direction to produce gas, the arebeing forced during its subsequent lateral movement in the oppositedirection toward the restricted portion of the slot, the

restricted portion preventing entry of the arc 15 therein duringrelatively high instantaneous values of arcing current, the arrangementbeing such that the produced gas is utilized to eflect I the restrictedportion.

the extinction of the arc after it has entered the restricted portion.

20. In an alternating current circuit interrupter, means forming a slothaving a restricted portion, venting means disposed adjacent therestricted portion, means for establishing an are within the slot, meansproviding a unidirectional magnetic field for causin a lateraloscillation of the arc within the slot, gas producing substance withwhich the arc contacts during its lateral movement in one direction toproduce gas, the arc being forced into the restricted portion during itslateral movement in the opposite direction, and the produced gas passingout of the slot through the venting means to facilitate the extinctionof the arc after the latter has entered WINTHROP M. LEEDS.

